1. Technical Field
The present invention relates to a switch unit, and particularly to a switch unit for preventing the generation of noise at the time of a switching operation.
2. Related Art
There are various types of switch units used in operation panels of various electronic devices, such as seesaw type switches that are a combination of a switch knob having a fulcrum at a central section and a tact switch, and a type that has a fulcrum at one end of a switch knob and is operated at the other end. In particular, with the high functionality and divergence of various devices in recent years, switches with an automatic reset function, where a switch knob returns to its original position after the switch has been operated and a hand removed, are being widely used.
This type of conventional switch unit will be described using FIG. 6, FIG. 7 and FIG. 8. FIG. 6 is an upper external view of a conventional switch unit. FIG. 7 is a cross sectional view of the switch unit shown in FIG. 6 taken along line Dxe2x80x94D, and shows a stationary state where the switch is not operated. FIG. 8 is a cross sectional view of the switch unit shown in FIG. 6 taken along line Dxe2x80x94D, and shows an operation state where the switch has been operated. These drawings show examples of a see-saw type switch unit.
The conventional switch unit is provided with a switch knob 12 capable of being tilted with a rotational shaft 11 in switch housing 10 as a center, and a switch operation is carried out by the switch operator pressing the upper surface of this switch knob. The switch operator performs ON and OFF operations of the switch unit by pressing close to the two ends of the switch knob 12, but a projection 13 is formed on a rear side of the section on the switch knob 12 pressed by the switch operator. This projection 13 is provided in order to supply pressing force to a resin type tact switch 15 fixed to a printed substrate 14, and this pressing force is exerted via a switch shaft 16 arranged by the tip of the projection 13. The switch shaft 16 has movement in the lateral direction regulated by a guide rail 17, and it is possible to always exert pressing force in a direction vertical with respect to the tact switch 15.
The tact switch 15 merely transmits an electrical signal to an ON/OFF hold circuit, not shown, in response to pressure from the switch operator, and the ON/OFF hold circuit (not shown) carries out switch turnover/detent. In this way, electrical signals are transmitted to an electronic device (not shown) etc. connected to the switch unit, and it is possible to carry out ON/OFF switching.
If the switch knob 12 is operated by a switch operator, the switch unit is put into a state as shown in FIG. 8, but when the operator releases the switch knob 12, the switch knob 12 will immediately return to the original position shown in FIG. 7. This automatic reset function is well known in the related art, and so detailed description will be omitted, but uses, for example, restoration force of a flexible switch (refer to Japanese Patent Laid-open Publication No. Hei 11-86683 for example), or causes restoration to an original position by providing a spring at a connecting section of a rotational shaft 11 and the switch knob 12 and utilizing resilient force of this spring.
However, with the above described switch unit of the related art, there is a problem in that when the switch knob 12 is restored to the original position, noise is generated as a result of the tip of the projection 13 hitting the switch shaft 16. In order to solve this problem, it has been considered to adopt a switch unit using a push-pull switch such as that disclosed in Japanese Patent Laid-open Publication No. Hei 11-86683, but it is necessary to change the structure of the switch unit significantly, and is not a realistic solution because it causes increase in cost.
The present invention is intended to solve the above described problems, and an object of the present invention is to provide a switch unit that does not significantly change a switch structure, suppresses striking noise generation and has a quiet operating sound.
In order to solve the above described problems, a switch unit of the present invention comprises a switch knob arranged capable of being tilted with a rotational shaft as a shaft center and provided with an automatic reset function for restoring to an original position, a switch shaft connection shaft provided on the switch knob, a switch shaft being moved in accordance with an inclination restoration operation as a result of connecting to the switch shaft connection shaft, a guide rail for guiding movement of the switch shaft in a straight line, and a tact switch, arranged capable of connection and disconnection to and from the switch shaft, for electrical connection and disconnection as a result of pressure from the switch shaft, wherein the tact switch has a region pressed from the switch shaft constituted by a resilient member.